Prolonged Red Persistent Luminescence in Bi3+ Single-Doped LiGa5O8: Regulating Traps by Site Selective Occupation

Persistent luminescence (PersL) materials with impressive superiorities in optical performance have shown tremendous potential for information encryption application. Herein, a Bi3+-doped LiGa5O8 PersL material is facilely synthesized by a simple solid-state reaction. Site selective and preferential occupation of Bi3+ ions at distinct Ga3+ and Li+ polyhedra sites in LiGa5O8 endows it with a bimodal emission at 511 and 718 nm upon UV excitation at 254 nm. After removing the light source, an intense red afterglow was observed due to the generation of more and deeper traps classified as the oxygen vacancy defect (VO••) and the impurity defect (BiLi••). It is rarely reported in inorganic phosphors to achieve the Bi3+ single doping-activated red PersL. The LiGa5O8:x% Bi3+ (with x = 0.5-5.0) samples also exhibit tunable PL and time-dependent PersL properties. Combined with the Morse Code, a multiple information encryption model based on the abnormal optical properties of LiGa5O8:x% Bi3+ (x = 0, 0.5, and 5.0) samples was designed for high-level dynamic anticounterfeiting. These achievements further validate the use of the Bi3+ single doping strategy to explore excellent PersL materials and expand their multifunctional optical applications.